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Full text of "Treatise On Applied Analytical Chemistry(Vol-1)"

39«

COLZA OIL AND  OTHER CRUCIFEROUS  OILS

3. FACHINI AND DORTA'S METHOD.1—This is based on the insolubility
in acetone of the potassium salts of the solid fatty acids.

10 grams of the fatty acids obtained from the oil in the usual way are
dissolved in 90 c.c. of pure, boiling acetone, the boiling solution being
treated with 10 c.c. of aqueous N-caustic potash solution and allowed to
cool to about 15°. The precipitate formed is collected on a dry filter, freed
from liquid by suction, washed with small portions of pure acetone and
then decomposed with a dilute acid to liberate the fatty acids, which are
dissolved in petroleum ether. The solution is filtered and evaporated and
the arachidic and lignoceric acids investigated by precipitation from- 90%
alcohol in the manner of the Tortelli and Ruggeri method.

2. Detection of Adulterations.—Commercial arachis oil may be
adulterated with, or may contain as impurities, sesame, cottonseed, colza,
poppyseed and other seed oils. Sesame" and cottonseed oils are detected
by the reactions of Villavecchia and Fabris and of Halphen (see Sesame
Oil and Cottonseed Oil), colza oil by Tortelli and Fortini's reaction and
by a lowering of the saponification number [see Colza Oil), poppyseed oil
and other seed oils in general by the colour reactions of Heydenreich,
Hauchecorne, and Brulle, and by a diminution in the content of arachidic
and lignoceric acids.

*
* *

Comestible arachis oil, when fresh, should contain only traces of free acids,
Old oils and those for industrial use are more or less acid and may contain up
to about 30% of free acid (calculated as oleic acid), the usual proportion being
about 20%. Arachis oil for soapmaking should contain not more than i%
of moisture and foreign matters together and should have D =0-919-0-921,
iodine number 87-100, solidification point of the fatty acids 28-32-5°, Maumene
number (Tortelli) 50-6.

The following products are also sold : Arachis margarine, produced by
pressing the oil in the cold (m.pt. 22-25°, iodine number 79-80), arachis grease,
produced by purifying the rancid oil with soda and composed of sodium soap,
neutral oil and various impurities ; and arachis oil No. 2, obtained by the puri-
fication of rancid oils with ammonia. The commercial value of the grease and
of the oil No. 2 depends on the content of total fatty matter (see General Part,
i,-A and C).

COLZA OIL AND OTHER CRUCIFEROUS OILS.

The more common oils of the Craciferag are colza and ravison oils ;
less common are those of jambo, turnip, mustard (white and black), radish
seed and hedge mustard. All have very similar characters and properties.

Colza oil and ravison oil (from the seeds of Brassica campestris and B.
napus), which are most used, are yellow, sometimes tending to brown ; they
have a special, more or less pronounced odour and a slightly acid taste.
About 8 grams dissolved in 1000 c.c. of absolute alcohol at 15°. Their
characters are given later in Table XLIV.

With Heydenreich's reagent they give orange colorations with fairly
apparent brown striae, especially if the containing dish is moved slowly.
With Hauchecorne's and Brulle"'s reagents they give more or less deep orange
colorations.

1 Rend. Soc. chim. ital., 1910, p. 248, and 1912, p. 51 ;  Chem. Zeit., 1914, p. 18,d (Ann. de Chim. analyt., 1899, 4)